1. Field of the Invention
This invention relates to thickening agents useful for thickening a composition containing an oily base. The present invention also relates to compositions which contain such a thickening agent and an oily base.
2. Discussion of the Background
As a thickening agent or a solidifying agent for an oily base that is not soluble in water, a polyamide resin, 12-hydroxystearic acid, fatty acid dextrin, fatty acid inulin, fatty acid glycerin, dibenzylidene-D-sorbitol, acylamino acid, an acylamino acid amine salt, and the like have heretofore been known in general. However, although these thickening agents or solidifying agents are capable of thickening or solidifying specific oily agents, they are not capable of thickening or solidifying a wide variety of oily agents.
In the case of using an acylamino acid as a solidifying agent (see, JP-A-51-91884), the obtained gel composition is not smooth when applied to the skin and does not provide a good feeling in use.
Also, in the case of using acylalanine among acylamino acids as a thickening agent (see, JP-A-2004-100826), although acylalanine thickens silicone, acylalanine is not always satisfactory since it requires strong stirring during cooling in preparation of a gel oil.
The use of an acylamino acid amine salt as a gelatinizing agent has been known (see, JP-A-51-19139). Although an alkylamine salt is used as the amine salt of acylamino acid, the amine salt is considerably limited in the types of oily agents it can gelatinize, and the capability of the amine salt as a thickening agent is not always satisfactory since it is necessary to reinforce its gelatinizing capability by using waxes such as vaseline, lanoline, beeswax in combination in an amount of several times that of the amine salt in the case of using the amine salt for cosmetics such as a hair-styling agent and a cleansing gel.
Cosmetics containing N-acyl-L-glutamic acid dibutylamide have been reported as a gelatinizing agent (see, JP-A-2002-31697). N-acyl-L-glutamic acid dibutylamide is known to gelatinize various oily agents such as a hydrocarbon oil, an ester oil, and a silicone oil. However, the cosmetics have problems of: a low solubility to ordinary oily agents; a high temperature of about 150° C. is required for dissolving the gelatinizing agents; and they are not smooth when applied to the skin due to a hard and crumbly form of the obtained thickening composition.
Thus, there has been a strong demand for a thickening agent capable of thickening a wide variety of oily bases including a hydrocarbon oil and silicone as well as of generating a thickening composition having a practical dissolution temperature and excellent comfortableness in use.